Recent experimental observations have demonstrated that effective pulmonary ventilation can be achieved in dogs by using small tidal volumes, less than the deadspace volume, at high respiratory frequencies, above 4 Hz; however, the physical basis for this gas exchange is not known. We have confirmed these observations by demonstrating effective CO2 removal in dogs with ventilation consisting of tidal volumes of less than 50% of the deadspace (equipment plus anatomic) volume at frequencies of 12-20 Hz. In addition we have developed an elementary theory, based on the concept of facilitated diffusion, which can in part explain the frequency, tidal volume, and lung volume dependence of CO2 removal we observed. We propose herein to examine, in a more comprehensive manner, the physical bases of gas exchange by this technique in anesthetized dogs. The frequency, oscillation volume, lung volume, and gas physical property dependence of gas exchange by this technique will be examined first in normal dogs and later after experimental induction of airway and airspace pathology. Theoretical concepts to explain our observations will be developed on our theoretical work or hardware models studies will be tested in the animal models in vivo. The overall goal of this combined theoretical, physical model, and animal study is to obtain a comprehensive understanding of the conditions which affect high frequency, low tidal volume, ventilation, so that this technique may be most usefully applied to the ventilatory support of patients with respiratory disease.